Refrigerating device

ABSTRACT

A refrigeration unit for performing a refrigerating cycle by circulating R32 as a refrigerant through a refrigerant circuit composed of a compressor ( 23 ), a condenser ( 22 ), expansion means ( 26 ), and an evaporator ( 2 ). An amount of R32 for filling the refrigerant circuit is set to be in a range of 120 g to 450 g per kW of refrigerating capacity, or an amount of R32 for filling the refrigerant circuit is set to be in a range of 400 g to 750 g per liter of unobstructed capacity of the condenser ( 22 ). By using R32 as a refrigerant that is small in Global Warming Potential (GWP), an energy-saving refrigeration against global warming with high coefficient of performance (COP) is obtained.

This application is the national phase under 35 U.S.C. §371 of PCTInternational Application No. PCT/JP00/07068 which has an Internationalfiling date of Oct. 12, 2000, which designated the United States ofAmerica.

TECHNICAL FIELD

The present invention relates to a refrigeration unit, and moreparticularly relates to a refrigeration unit with use of R32 (chemicalformula: CH₂F₂) as a refrigerant alternative to R22 (chemical formula:CHCIF₂) or with use of mixed refrigerants containing at least 70 weightpercent R32.

BACKGROUND ART

Global environmental challenges relating to refrigeration units or airconditioners that perform a refrigerating cycle with use of refrigerantsinclude (1) ozonosphere protection, (2) energy conservation, (3)measures against global warming (emission control of CO₂ ant the like),and (4) recycling of resources.

In the global environmental challenges, particularly in view of theozonosphere protection, R22 (HFC22) is high in ODP (Ozone DepletionPotential) so that it is not regarded as a preferable refrigerant.Accordingly, as prospective refrigerants alternative to R22, there areR410A (HFC32:HFC125=50:50 (weight ratio)) and R407C(HFC32:HFC125:HFC134a=23:25:52 (weight ratio)). Some refrigeration unitsfor performing a refrigerating cycle with use of R410A or R407C haveachieved the same COP (Coefficient of Performance) as R22, and havealready been manufactured as products.

As for energy conservation, there has already been notified thatdesignated air conditioners are required to improve COP by approx. 4% bythe end of September, 2004 (Notification No. 190 of the Ministry ofInternational Trade and Industry based on “Law concerning the RationalUse of Energy”). Therefore, in view of energy conservation, it isnecessary to use refrigerants having a large COP value.

In addition, demands for prevention of global warming is becomingharder. In the field of refrigeration units or air conditioners, anindex to global warming called TEWI (Total Equivalent Warming Impact) isused to evaluate the refrigeration units and air conditioners. The TEWIis expressed as the sum of an impact of refrigerants released to the air(direct impact) and energy consumption of a unit (indirect impact). Thedirect impact includes GWP (Global Warming Potential), while theindirect impact includes a reciprocal of COP. Consequently, in order toprevent global warming, or equivalently, to decrease the value of TEWI,it is necessary to select refrigerants having a small GWP value and alarge COP value.

The GWP values of R407C and R410A are 1980 and 2340, respectively, whichare slightly larger than the GWP value 1900 of R22. Accordingly, R32(HFC32) is expected as a prospective refrigerant having a small GWPvalue for prevention of global warming. R32 has the GWP value of 650,which is about one third of the GWP values 1900, 1980 and 2340 of R22,R407C and R410A, and therefore considered to be an extremely smallvalue.

The COP values of R407C and R410A are approximately equal to the COPvalue of R22, whereas the COP value of R32 is not larger than that ofR22. More particularly, although the refrigeration unit for performing arefrigerating cycle with use of R32 is theoretically expected a high COPvalue because of the characteristics of R32, any actual result thatsignificantly exceeds the COP of R22 is not provided so far. Also, useof R32 brings about a phenomenon of higher pressure and higher dischargetemperature compared to use of R22. In addition to that, there is aproblem of difficulty in reaching a safety consensus because R32 hasslight flammability. Because of this reason, the industrial society hasnot adopted R32 as an alternative refrigerant product.

DISCLOSURE OF INVENTION

Accordingly, it is an object of the present invention to provide anenergy-saving refrigeration unit against global warming that is capableof achieving high COP (Coefficient of Performance) with use of R32having a small GWP (Global Warming Potential) as a refrigerant.

The present invention is invented based on finding by an inventor of thepresent invention that a tendency for the COP of a refrigeration unit tochange in response to an amount of a refrigerant (the total amount forfilling a refrigerant circuit) is considerably different in types ofrefrigerants, especially between R32 and other refrigerants includingR410A. More particularly, as shown in FIG. 1a, in the case of using, forexample, R410A, there is a tendency that the COP gradually rises andsaturates with increase of an amount of the refrigerant within the rangeshown in the drawing. On the contrary, in the case of using R32, thereis a tendency that the COP marks a peak with change of an amount of therefrigerant, and then shows a sharp drop once an amount of therefrigerant is out of the range that gives the peak. Conventionally, thereason why use of R32 fails to provide high COP compared to use of R410Ais because the refrigerants are used in the range that is relativelylarge in amount of the refrigerant (1200 g to 1300 g in the case shownin FIG. 1a). The notable point here is that a peak value of the COP inthe case of using R32 with change in amount of the refrigerant is muchhigher than the COP in the case of using R410A with an optimum amount ofthe refrigerant (1300 g in the case of FIG. 1a). This indicates that useof R32 with an amount of the refrigerant set in an appropriate rangeenables achievement of high COP.

As described above, R32 has GWP much lower than that of conventional R22and R410A (about one third). Further, adequate selection of an amount ofthe refrigerant enables R32 to obtain COP higher than that of R410A andR22. This makes TEWI (Total Equivalent Warming Impact) of R32 smallerthan the TEWI of R22 and R410A, thereby proving superiority of R32 inglobal warming characteristics compared to R22 and R410A.

The present invention provides a refrigeration unit for performing arefrigerating cycle by circulating R32 as a refrigerant through arefrigerant circuit comprising a compressor, a condenser, expansionmeans, and an evaporator, wherein an amount of R32 for filling therefrigerant circuit is in a range of 120 g to 450 g per kW ofrefrigerating capacity.

As shown above, an amount of R32 for filling the refrigerant circuitbeing in the range of 120 g to 450 g per kW of refrigerating capacityimplements high COP.

Herein, measuring method of refrigerating capacity (kW) shall conform tothe regulations of Japan Industrial Standard (JIS) C9612.

It is noted that since an amount of R32 for filling is “in the range of120 g to 450 g per kW of refrigerating capacity”, the total amount ofR32 for filling the refrigerant circuit is, for example, 600 g to 2250 gif the refrigerating capacity is 5 kW.

The present invention also provides a refrigeration unit for performinga refrigerating cycle by circulating R32 as a refrigerant through arefrigerant circuit comprising a compressor, a condenser, expansionmeans, and an evaporator, wherein an amount of R32 for filling therefrigerant circuit is in a range of 400 g to 750 g per liter ofunobstructed capacity of the condenser.

As shown above, an amount of R32 for filling the refrigerant circuitbeing in the range of 400 g to 750 g per liter unobstructed capacity ofthe condenser implements high COP.

It is noted that the reason why an amount of R32 for filling therefrigerant circuit is prescribed as “per liter unobstructed capacity ofthe condenser” is because the unobstructed capacity of the condenser isdominant over an amount of the filling refrigerant.

Also, since an amount of R32 for filling is “in a range of 400 g to 750g per liter of unobstructed capacity of the condenser”, the total amountof R32 for filling the refrigerant circuit is, for example, in the rangeof 600 g to 1125 g if the unobstructed capacity of the condenser is 1.5liter.

The principles of the invention are not only applicable to a singlerefrigerant of R32, but also applicable to mixed refrigerants containingat least 70 weight percent R32.

The present invention also provides a refrigeration unit for performinga refrigerating cycle by circulating mixed refrigerants containing atleast 70 weight percent R32 through a refrigerant circuit comprising acompressor, a condenser, expansion means, and an evaporator, wherein anamount of the R32 for filling the refrigerant circuit is in a range of84 g to 450 g per kW of refrigerating capacity.

In the case of using mixed refrigerants containing at least 70 weightpercent R32 as shown above, an amount of R32 for filling the refrigerantcircuit being in the range of 84 g to 450 g per kW of refrigeratingcapacity implements high COP.

The present invention also provides a refrigeration unit for performinga refrigerating cycle by circulating mixed refrigerants containing atleast 70 weight percent R32 through a refrigerant circuit comprising acompressor, a condenser, expansion means, and an evaporator, wherein anamount of the R32 for filling the refrigerant circuit is in a range of280 g to 750 g per liter of unobstructed capacity of the condenser.

In the case of using mixed refrigerants containing at least 70 weightpercent R32 as shown above, an amount of R32 for filling the refrigerantcircuit being in the range of 280 g to 750 g per liter of unobstructedcapacity of the condenser implements high COP.

BRIEF DESCRIPTION OF DRAWINGS

FIGS. 1A and 1B are views showing the results of measuring COP in thecase of using R32 as a refrigerant and COP in the case of using R410A asa refrigerant, each with an amount of the refrigerant (the total amountfor filling the refrigerant circuit) changed in cooling operation, whereFIG. 1A shows the result in cooling operation and FIG. 1B shows theresult in heating operation;

FIG. 2 is a view showing outline structure of a heat pump type airconditioner in one embodiment of the present invention;

FIGS. 3A and 3B are views showing comparison of COP in the case of usingR32 and COP in the case of using R410A under conditions of equalcapacity (equal in compressor capacity), where FIG. 3A is a view showingcomparison of COP of R32 and R410A in percentage, and FIG. 3B is a viewshowing the comparison in measured values;

FIGS. 4A, 4B and 4C are views each showing setting values ofunobstructed capacity of an indoor heat exchanger and unobstructedcapacity of an outdoor heat exchanger of the air conditioner:

FIG. 5 is a view showing a content and energy efficiency of R32 in mixedrefrigerants of R32 and R125;

FIG. 6 is a view showing COP against an amount of refrigerants R32 andR410A in cooling and heating; and

FIG. 7 is a view showing capacity of an accumulator and a receiveragainst the refrigerating capacity of each of refrigerants R32, R410Aand R22.

BEST MODE FOR CARRYING OUT THE INVENTION

Detailed description will now be given of a refrigeration unit inembodiments of the present invention with reference to drawings.

FIG. 2 shows outline structure of a heat pump type air conditioner inone embodiment of the present invention. In the air conditioner, anoutdoor unit 20 and an indoor unit 1 are connected by refrigerant pipes41 and 42 to constitute a refrigerant circuit, through which R32 iscirculated as a refrigerant. The indoor unit 1 accommodates an indoorheat exchanger 2. The outdoor unit 20 accommodates a compressor 23 forcompressing and discharging a refrigerant (R32), a four-pass divertervalve 25 for diverting refrigerant passes, an outdoor heat exchanger 22,a motor-driven expansion valve 26, and an accumulator 24 forvapor-liquid separation of the circulated refrigerant.

In cooling operation for performing the refrigerating cycle, byswitching setting of the four-pass diverter valve 25, a refrigerantdischarged by the compressor 23 is sent, as shown with a solid line inFIG. 2, through a pipe 31, the four-pass diverter valve 25 and a pipe33, to the outdoor heat exchanger 22 functioning as a condenser. Therefrigerant condensed in the outdoor heat exchanger 22 is sent through apipe 36, an expansion valve 26 for tightening the pass to expand therefrigerant and a pipe 42, to the indoor heat exchanger 2 functioning asan evaporator. Further, the refrigerant evaporated in the indoor heatexchanger 2 is returned through a pipe 41, a pipe 34, the four-passdiverter valve 25, a pipe 32, an accumulator 24 and a pipe 35, to thecompressor 23. In heating operation, the four-pass diverter valve 25 isswitched to send a refrigerant discharged by the compressor 23 to theindoor heat exchanger 2 functioning as a condenser through the pipe 31,the four-pass diverter valve 25, the pipe 34 and the pipe 41, as shownwith a dotted line in FIG. 2. The refrigerant condensed in the indoorheat exchanger 2 is sent to the pipe 42, the expansion valve 26 in afull-open state, the pipe 36, and the outdoor heat exchanger 22functioning as an evaporator. Further, the refrigerant evaporated in theoutdoor heat exchanger 22 is returned through the pipe 33, the four-passdiverter valve 25, the pipe 32, the accumulator 24 and the pipe 35, tothe compressor 23.

For evaluating COP (Coefficient of Performance) of the air conditioner,the inventor of the present invention prepared air conditionersdifferent in capacity class from 2.2 kW to 5.0 kW with unobstructedcapacity of the indoor heat exchanger 2 and unobstructed capacity of theoutdoor heat exchanger 22 changed in variations as shown in FIGS. 4A and4B. FIG. 4C shows comparison of the unobstructed capacity of the outdoorheat exchanger 22 and the unobstructed capacity of the indoor heatexchanger 2. Unobstructed capacity of the entire refrigerant circuit ischanged according to setting of the unobstructed capacity of the indoorheat exchanger 2 and the unobstructed capacity of the outdoor heatexchanger 22.

For example, for the 5.0 kW class air conditioner, unobstructed capacityof the outdoor heat exchanger 22 is set to 1.45 liter and unobstructedcapacity of the indoor heat exchanger 2 is set to 0.47 liter. In the 5.0kW class air conditioner, COP was measured with an amount of arefrigerant (the total amount for filling the refrigerant circuit)changed. The result thereof is shown in FIGS. 1A and 1B, where FIG. 1Ashows COP in cooling operation and FIG. 1B shows COP in heatingoperation. As shown in FIG. 1A, in cooling operation, relatively highpeak COP values of 2.7 to 2.8 were obtained when an amount of therefrigerant was 960 g, whereas the air conditioner with the samecapacity of 5.0 kW and use of R410A showed COP of 2.2 at most (when anamount of the refrigerant was 1300 g).

Thus, it was attempted to find the range of an amount of the refrigerantthat gives a COP peak under each condition in the case of using R32. Asa result, it was found that the COP peak is given when an amount of R32for filling the refrigerant circuit is in the range of 120 g to 450 gper kW of refrigerating capacity, or an amount of R32 for filling therefrigerant circuit is in the range of 400 g to 750 g per liter ofunobstructed capacity of the outdoor heat exchanger 22.

Also, in the case of the same capacity (equal in compressor capacity) inthe range from 2.2 kW to 5.0 kW, COP with use of R32 and COP with use ofR410A were compared, and the result as shown in FIGS. 3A and 3B wereobtained. An amount of the refrigerant in the case of using R32 wasoptimized in the range of 60 wt. % to 80 wt. % against an amount of therefrigerant in the case of using R410A. FIG. 3A shows that the COP withuse of R32 was 108.1% when using the COP value with use of R410A as areference (100%). FIG. 3B shows that the COP with use of R410A was 4.00whereas the COP with use of R32 was 4.33. This implies that use of R32with an amount of the refrigerant set in an appropriate range enablesachievement of the COP much higher than that in the case of using R410A.The improvement of the COP may be attributed to small pressure loss andimproved heat transfer of the refrigerant in addition to improvedphysical properties of the refrigerant.

FIGS. 1A and 1B also indicate that an optimum amount of the refrigerantthat gives a COP peak in the case of using R32 was 960 g in coolingoperation and 840 g in heating operation, whereas an optimum amount ofthe refrigerant in the case of using R410A was 1300 g in coolingoperation and 1100 g in heating operation. As this result implies, acooling/heating ratio of an optimum amount of the refrigerant in thecase of using R32 is closer to 1 compared to the case of using R410A.This saves a cooling/heating refrigerant adjusting container andimplements decrease of accumulator capacity.

Although in the embodiment, description was made of the heat pump typeair conditioner, the present invention is naturally not limited thereto.The present invention is broadly applicable to the units for performinga refrigerating cycle with use of R32 as a refrigerant.

Also the principles of the present invention are not only applicable toa single refrigerant of R32, but also applicable to mixed refrigerantscontaining at least 70 weight percent R32. For example, a compound ofR32 and R125 is regarded as a mixed refrigerant. In the mixedrefrigerants of R32 and R125, the range having 70 weight percent R32 orless is an azeotropic range where the liquid composition and thegenerated vapor composition are identical, while other ranges arecategorized as a nonazeotropic range. With increase of a content of R32,properties of R32 are clarified, and in the nonazeotropic range, theproperties of R32 become remarkable.

Experiments performed by the present inventor confirmed that in the caseof using mixed refrigerants containing at least 70 weight percent R32,high COP is obtained if an amount of R32 for filling the refrigerantcircuit is in the range of 84 g to 450 g per kW of refrigeratingcapacity, or an amount of R32 for filling the refrigerant circuit is inthe range of 280 g to 750 g per liter of unobstructed capacity of thecondenser.

FIG. 5 shows relationship between a content of R32 in mixed refrigerantscontaining R125 and energy efficiency. With a content of R32 equal to 70weight percent or more, rise of the energy efficiency is remarkable.With a content of R32 beyond approx. 80 weight percent, the energyefficiency exceeds the energy efficiency of R22. Therefore, with acontent of R32 equal to 70 weight percent or more, high COP is obtained.

Thus, a single refrigerant of R32 or mixed refrigerants containing atleast 70 weight percent R32 are, as shown in FIGS. 1 and 5, have the COPequal to or higher than that of conventional refrigerants such as R22.Further, the GWP (Global Warming Potential) of R32 is as low as approx.one third of the GWP of conventional refrigerants such as R22 as statedbefore. Consequently, the TEWI (Total Equivalent Warming Impact) of R32is lower than the TEWI of R22 and R410A (lowering rate of 10 to 20%),thereby proving superiority of R32 in global warming characteristicscompared to R22 and R410A.

In view of the forgings, R32 refrigerant and mixed refrigerantscontaining at least 70 weight percent R32 are not only free fromdepleting ozonosphere but also small in GWP (Global Warming Potential)and TEWI (Total Equivalent Warming Impact) and large in COP (Coefficientof Performance), which makes them energy-saving refrigerants againstglobal warming.

Also, a refrigeration unit with use of R32 refrigerant is, as shown inFIG. 6, capable of obtaining high COP with an amount of the fillingrefrigerant smaller than that of R410 refrigerant, and small indifference between an optimum amount of the refrigerant in cooling andan optimum amount of the refrigerant in heating. More particularly, R32refrigerant is high in heat transfer capacity compared to R410Arefrigerant, capable of implementing sufficient capacity with a smallamount of the filling refrigerant, and small in difference between anoptimum amount of the refrigerant in cooling and an optimum amount ofthe refrigerant in heating compared to R410 refrigerant, which enablesreduction of an amount of the refrigerant for use in the refrigerationunit.

FIG. 7 shows capacity of an accumulator and a receiver against therefrigerating capacity of each of the refrigerants R32, R410A and R22.As shown in FIG. 7, the refrigeration unit with refrigerating capacityof 4 kW or less needs neither an accumulator nor a receiver. Therefore,the refrigeration unit with use of R32 saves an accumulator and areceiver, which enables reduction of production costs of therefrigeration unit as well as downsizing of the refrigeration unit.

What is claimed is:
 1. A refrigeration unit for performing arefrigerating cycle by circulating R32 as a refrigerant through arefrigerant circuit comprising a compressor (23), a condenser (22),expansion means (26), and an evaporator (2), wherein an amount of R32for filling the refrigerant circuit is in a range of 120 g to 450 g perkW of refrigerating capacity.
 2. A refrigeration unit for performing arefrigerating cycle by circulating R32 as a refrigerant through arefrigerant circuit comprising a compressor (23), a condenser (22),expansion means (26), and an evaporator (2), wherein an amount of R32for filling the refrigerant circuit is in a range of 400 g to 750 g perliter of unobstructed capacity of the condenser.
 3. A refrigeration unitfor performing a refrigerating cycle by circulating mixed refrigerantscontaining at least 70 weight percent R32 through a refrigerant circuitcomprising a compressor (23), a condenser (22), expansion means (26),and an evaporator (2), wherein an amount of the R32 for filling therefrigerant circuit is in a range of 84 g to 450 g per kW ofrefrigerating capacity.
 4. A refrigeration unit for performing arefrigerating cycle by circulating mixed refrigerants containing atleast 70 weight percent R32 through a refrigerant circuit comprising acompressor (23), a condenser (22), expansion means (26), and anevaporator (2), wherein an amount of the R32 for filling the refrigerantcircuit is in a range of 280 g to 750 g per liter of unobstructedcapacity of the condenser.